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Failed Smog Check Questions & Answers - Page 4

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Question: I have a 2003Toyota p/u with 160,000 miles.  The check engine light is on and I need to have my truck smogged this month.  The error codes are P0300, P0301 & P0303.  The engine has some misfiring.  I had the problem diagnosed and was told to expect to pay at least $4000 to correct burnt valve(s).  I took care of an earlier problem and replaced the O2 sensor.  I’ve driven the truck this way for nearly a year and want to get a little more use out of it without spending a fortune.What I don’t understand is IF the engine can pass the emissions test then why won’t the state pass it even though there is SOME misfiring?  That’s an expensive repair IF the emissions are within allowable limits.Is there any way to sell the truck – say if the buyer is willing to sign a statement that he’ll take responsibility for paying for all necessary repairs?
Answer: We'd recommend a second opinion. It's true the OBD 0300 codes are misfire related. However if in fact the cause are burnt valves you should see an absolute emissions increase. If in fact emissions are within limits yet the codes triggered indicate a misfire you may want to focus on the engine ignition system (spark plugs, coils).
As far as selling the truck without a smog check... We can't give legal advise... but we can say this, there really isn't much you can do to stop a buyer from suing you if they have a change of heart soon after buying the car (say they take the vehicle in for repairs and in fact it does need a valve job and it will cost $4000.00), because Section 24007 (b)(2) of the Vehicle Code states it is the responsibility of the seller to provide a valid smog certificate at the time of delivery of the vehicle. There is no provision in the law to sell a vehicle "as is" as far as the smog check is concerned.
Question: I have a question  about my Toyota Camry 1990  recently my mechanic did a mistake and broke the  oil pressure. This lock like sensor is located in front of the  top of the engine this person just sealed the little hole  but I must to do Smog Test now what should happen with this issue.

Answer: The Oil Pressure sensor is not "directly" an emissions component and will not effect the smog test, unless it's grossly leaking oil or causing the Check Engine light to illuminate.


Question (a): I purchased a 1996 Toyota P/U with a six cylinder 132K over the weekend the owner said he had forgot to smog it. I took it to the smog place yesterday and it failed (NOx) and they told me it most likely needes a cat converter.I then took it to two different shops that said the same thing so I have one put in and it failed again. Can you tell me what is nox and why it would fail. This truck has no egr VALVE FROM THE FACTORY. IT SAYS n/a ON THAT PART OF THE PAPER FROM THE SMOG REPORT. At this point I just want to get it fixed. The truck runs great and there is no check engine light on.

Question (b): Hi, I had my 99 Chevy Cavalier smogged and it failed. I have never had a car fail before. The mechanics don't tell me why it failed they just say it failed. the first time it passed at the 25 mph and failed on the 15 mph. Then they did a fuel injection flush and it failed on both accounts on the second time. What could the problem be? do I need to get a new cat converter? I am female so don't know a lot about this situation, plus i have never had a car fail the smog test.

Answer: Vehicles fail their smog inspection for different reasons based on the variety of emissions control systems used on production vehicles. We recommend using our SmogSmart VIR Report system. We'll be able to give you a much better idea of what your vehicle's emission problem might be. The SmogSmart VIR Report system will ask you to fill in all the information our report system & technicians need to effectively evaluate your vehicle's emissions failure. You may also use the "Additional Information" section of the blank form to include detailed comments. To obtain your vehicle's SmogSmart Report, please visit the On-Line Evaluations Page at



Answer: Code 33 & Code 34 relate to the MAF Mass Air Flow Sensor. Have this component diagnosed and if defective repaired.


Question: I HAVE AN 88 HONDA ACCORD "FUEL INJECTION" I Cant seem to pass the smog "test only" sensors operational but the gas level is at 8.0 when they should be at about 2.0 . mechani said its perfectly fine all sensors operational but the gas readings are still very high. Will making a hole between the catalizer & muffler help?

Answer: No, holes will not help, in fact they may be considered TAMPERS and definitely cause a smog failure even if emissions are lowered (which making hole will NOT do). Your best bet is the find a mechanic, a smog check repair mechanic, which can diagnose this problem and pin point the exact fault, whether sensor related or not.


Question: i just passed every component of my smog test except that the OBDII component "could not be completed". i have a 96 Saab 900s. the mechanic couldn't really explain the problem, but advised me to drive my car for the next 2-3 days - particularly freeway driving - and then have it retested.

Answer: If you own a 1996 or newer vehicle (which a apparently you do) you own a vehicle which is equipped with an On-Board Diagnostics system called OBD II, as opposed to an OBD I system which older vehicles were equipped with. The OBD II Diagnostic system is designed to monitor all aspects of your engine's emission conditions and report this information to a central database within it's computer. This information is processed and checked against the computers pre-determined values for various inputs levels and performance patterns. If any problems are found, the computer will determine whether to alert the driver or not.
If a decision has been made to alert the driver of an emissions problem, the "Check Engine" or "Engine Malfunction" light will illuminate on the vehicle's dashboard. In more serious emission conditions the computer may even begin to rapidly flash the "Check Engine/Malfunction" light indicating to the driver, that the vehicle needs immediate diagnosis/repair attention.
Now here's what the smog test has to do with the OBD II system...Your vehicle is equipped with an OBD II computer AND a link to connect the OBD II computer to a Smog Check Analyzer or Data Scan Tool (available at most auto part stores). The OBD II link relays all "Check Engine" conditions along with stored Trouble Codes with in the center database, to the smog machine during the time of the smog inspection. If any codes are present which cause the Check Engine light to illuminate either regularly or intermittently, the vehicle fails the smog inspection. Here's the tricky part, not all computer codes illuminate the Check Engine light. In fact I can say there are two types of codes, bad codes and good codes.
The good codes are the "Readiness Flags". These Readiness Flags indicate that certain emissions systems which the OBD II computer has been monitoring have PASSED the test, indicating that those systems are working properly. Then there are the bad codes. The bad codes are actual "Trouble Code". These codes indicate that the OBD II computer has detected a problem with in the emissions system. The Trouble Code will specifically indicate the component and problem which was found. Newer vehicle's have very complex codes in the thousands.
A vehicle will fail the smog inspection if the proper "Readiness Flags" are not set. A vehicle will also fail the smog inspection if any "Trouble Codes" are present. So it is possible for a vehicle to fail the smog inspection without the "Check Engine" light on. "Readiness Flags" do not cause the "Check Engine" light to illuminate, but may cause a vehicle to fail the smog test.
Now here's the fix... in order to set all the proper "Readiness Flags" the OBDII system must complete at least one drive cycle (in some cases two or three).  A drive cycle is a sequence of internal tests which the OBDII computer runs while your vehicle is being driven. This insures all emissions systems are functioning properly. Only then will your vehicle pass the smog inspection. A drive cycle usually requires one week of driving.


Question: My 2000 Lexus LS400 just failed the SMOG check (This has never happened before so I guess I was complacent and ignorant about preparation). For example, I didn't know that it was important to run the car for 20-30 minutes before arriving at the SMOG test station. I drove it 3-5 minutes max after it had been sitting around all day (end of the work day). Now they say I have to pay $120 for an inspection and then there is the cost of repairs (needless to say I don't trust auto mechanics, they are probably soo psyched I failed)! Is it possible to do it right (change my oil, take my car in only after it is warm etc) and then get it retested (ie. redo the smog test just days later)? It barely failed: NOx (PPM) MAX 835 AVE 237 MEAS 847.

Answer: 847 NOx is pretty high, and consider this... NOx is created when the engine's combustion chambers passes 2500f, so warming up your car for 20-30 min will not help in this case. Vehicles fail their smog inspection for different reasons based on the variety of emissions control systems used on production vehicles. You will more then likely end up having the pay a smog repair station for a diagnosis, hopefully it will be a simple problem to fix.
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